Electrophotographic image forming devices (“EP devices”), such as photocopiers, laser printers, and facsimile machines, may employ the use of a removable toner cartridge assembly containing a fixed supply of toner. As pages become printed, this toner supply decreases. At some point the toner supply becomes so depleted that the quality of the printed pages deteriorates and the cartridge must be replaced. Often times, the onset of the low toner supply comes suddenly. This may present a suboptimal situation for a user who does not have a replacement cartridge at hand. Namely, the user will not be able to resume printing high-quality printed pages until he or she obtains a replacement cartridge. This may result in a period of downtime when the printer is substantially unusable.
Additionally, manufacturers desire methods for estimating the number of printed pages remaining on a given toner cartridge. For instance, when establishing a default supply yield or yield range for a given model of cartridge during testing, manufacturers require accurate methods for estimating the total number of printed pages remaining on a toner cartridge.
To address these issues, several methods have been contemplated for estimating the total number of printed pages that can be produced with a toner cartridge or are remaining on a given toner cartridge. One method simply counts the pages printed and compares this amount to a predetermined value. If the number of pages printed exceeds the predetermined value, a message may be generated informing a user to replace the toner cartridge. Instead of using a predetermined value, other methods compare the number of pages printed with a fixed, estimated amount of toner used per page. Unfortunately, these methods cannot adapt for the specific type of printing being conducted by the user. For instance, a user that prints mostly text documents may use less toner than a user printing complex graphical images. Accordingly, these static methods often produce spurious results that provide incorrect information on the remaining life of a toner cartridge. Also, these methods rely on an actual page count of the number of pages printed, which may also contribute to suboptimal results.
Accordingly, the need exists for a method for determining the number of printed pages remaining in a removable toner cartridge for an EP device. The method would not depend on the actual number of pages printed, but would take into account other variables, including the amount of toner used per individual page. Also, the need exists for a toner cartridge and/or EP device capable of storing and/or performing such a method.